1. Technical Field of the Invention
The present invention relates to shaped articles, especially opaque packaging shaped articles such as bottles, allowing certain products, such as milk, to be stored away from visible and UV radiation.
This invention relates more particularly to opaque bottles obtained by the injection-blow molding of a polyester-based composition and to a process for manufacturing the packaging articles, especially bottles.
2. Description of Background and/or Related and/or Prior Art
Bottles made of thermoplastics, and more particularly polyester such as polyethylene terephthalate, are being increasingly used for the storage of diverse and varied liquids, especially liquid food products such as water, beer, and still or fizzy sugared drinks, generally called carbonated drinks. They are also used for the storage of milk and other solid or liquid food substances.
However, milk may come in various forms, depending on the treatment process applied, allowing it to be preserved for relatively short or relatively long periods. Thus, sterilized fresh milk must be used very soon after being bottled, whereas UHT (ultra-high temperature) milk can be preserved for several months after being bottled.
This very long preservation time imposes constraints on the storage container, such as bottle or carton.
This is because the taste of milk changes through the effect of UV and/or visible radiation. A milk having its taste impaired by this effect is termed as having a “light-affected taste”.
This change is especially due to the degradation of vitamin B2 (riboflavin) in milk as a result of being exposed to light. The degradation of this vitamin in milk varies according to the intensity of the light source, to the exposure time and also to the wavelength range of the light source.
Radiation with wavelengths from 350 to 520 nm appear to be responsible for the degradation of this vitamin and therefore for the impairment in the taste of the milk.
Consequently, storage containers or the packaging for these containers must have a very low or zero light transmission for radiation with wavelengths of shorter than 550 nm, and more generally for UV radiation, and visible radiation. This specification is increasingly important as the storage time of the milk is extended.
This constraint is very important for long-life milk, such as UHT (ultra-high temperature treatment) milk, and also for certain types of vitaminized milk that is sensitive to radiation and for derived dairy products, such as yogurt, cream or the like.
Solutions for the production of containers compatible with the long storage time of milk have already been proposed and are widely used.
One of the containers most used is a carton made of multilayer cardboard for ensuring low light transmission for the UV and visible wavelength ranges.
However, the closure systems of these cartons, especially after a first use, are not practical and do not guarantee effective closure.
To remedy the drawbacks of these cartons, such as stiffness, dead space, shape, size and handleability, it has been proposed to use bottles, especially bottles made of high-density polyethylene (HDPE).
However, to obtain a low light transmission level these bottles are formed by multilayer walls that may comprise three to six layers produced in different ways.
The external layers generally contain a white pigment, consisting of titanium oxide, in order to give an attractive appearance compatible with the product stored.
As an intermediate layer, there is a layer with a low light transmission. This layer generally includes a carbon black as light-absorbent filler. Finally, an oxygen barrier layer may also be present, and also adhesive layers in order to give the structure good stability.
These bottles require complex manufacturing processes. Furthermore, their recovery and recycleability are difficult to implement owing to the presence of several different materials.